1. Field of the Invention
The present invention relates to metal organic chemical vapor deposition equipment, and particularly relates to metal organic chemical vapor deposition equipment for forming a nitride semiconductor layer.
2. Description of the Background Art
A Metal Organic Chemical Vapor Deposition (MOCVD) method is one of the typical chemical vapor deposition methods, in which a Group III organic metal is vaporized and then thermally decomposed at a surface of a substrate, and reacted with a Group V gas to form a film. This method enables control of a film thickness and a composition, and is excellent in productivity, so that it is widely used as a film formation technique in manufacturing semiconductor equipment.
MOCVD equipment used in the MOCVD method includes a chamber, a susceptor disposed in the chamber, and a conduit for allowing a reactant gas to flow at a surface of a substrate. In the MOCVD equipment, a film is formed by holding the substrate on the susceptor, heating the substrate to an appropriate temperature while bringing the chamber into a reduced pressure state, and introducing an organic metal gas to the surface of the substrate through a conduit. At this time, in order that the formed film has a uniform thickness, the MOCVD equipment is required to allow the reactant gas to flow uniformly along the surface of the substrate. To do so, various shapes of conduits have been proposed in the MOCVD equipment.
As conventional MOCVD equipment, Japanese Patent Laying-Open No. 2-291113, for example, discloses chemical vapor deposition equipment having an introduction pipe introducing a reactant gas to above a substrate. The introduction pipe has a sample holding chamber accommodating a susceptor therein, a bottleneck portion having a cross-sectional shape long along a width direction of the substrate and short and flat along a height direction of the substrate, and blowing a reactant gas onto the substrate from a side of the substrate, and a guide portion located above the substrate and uniformly covering the substrate on its top side with a gap approximately equal to a width of the bottleneck portion in a width direction or with a gap decreased toward a downstream side of the reactant gas so as to guide the reactant gas along the surface of the substrate. The susceptor is fixed to the sample holding chamber, and holds the substrate on the downstream side of a reactant gas flow.
Furthermore, Japanese Patent Laying-Open No. 6-216030, for example, discloses compound semiconductor chemical vapor deposition equipment having a flow channel for introducing a reactant gas onto a substrate. The flow channel has a taper, a width of which in a height direction is decreased from an upstream side to a downstream side. A susceptor is fixed to a lower part of the taper.
Moreover, Japanese Patent Laying-Open No. 2-291114 discloses chemical vapor deposition equipment including a rotary susceptor for holding a substrate, and a liner pipe for introducing a reactant gas to the substrate. The liner pipe has a height monotonically decreased over the entire channel for introducing the reactant gas.
The MOCVD equipment is required to improve film formation efficiency. Upsizing of the susceptor enables formation of a large-diameter substrate as well as simultaneous heating of multiple substrates, and hence film formation efficiency would be improved. However, upsizing of the susceptor increases a distance between an upstream side and a downstream side of the susceptor, resulting in that the conditions of the reactant gas (e.g. a concentration, a temperature and the like of the reactant gas) between the upstream side and the downstream side of the susceptor are significantly different. As a result, there arises a problem of nonuniform thickness of a formed film. As such, it is not conventionally possible to improve film formation efficiency while allowing the formed film to have a uniform thickness.